Brake shoe and head arrangement



March 23, 1948.

c. E. TACK 2,

BRAKE SHOE AND HEAD ARRANGEMENT Filed July 8, 1944 Patented Mar. 23, 1948 Carl Tack, Chicago,

Steel Foundries, Chic New Jersey Ill.

, assignor to American,

ago, 111., a corporation of.

Application'July 8, 1944, Serial No. 544,009 12Clainis.. (Cl. 188--234) My invention.v relates. to-.braking. means and.

more particularly to a novel formofbrake shoe or brake block.suitableforspecial application and particularly adaptedsfor railwayv brakes of the type commonly designated drumor disc, wherein,

one'or more rotatable elements .may. be supported on, awheel and, axleassembly. and provided.

with suitable. braking surfaces...

Experience, and theoretical studies.v as well, have proved that metal .to. metalbrakes function in. somewhat different. manner. as compared with brakes composed, of. composition. material. against metal. The ordinary. railway brake, oi course, is composed ofmetalto metal while thetype of brake. with;which .Weare -.here primarily con.-v cerned consists ofsome .formef composition ma. terial bearing. against: metal.v The .composition.

material, of. course,..as..a..rule-.contains. more or. lessmetal, which acts as a mechanical bond, preventingseparation, and also servesto stabilizethe friction coefiicient:

Theso-called brake-:block. which may be of Various types of.- composition. hasHa-tendency when-in use to heat excessively inlocalized areas. The exact causes of this are not altogether clear but it-is. well. known that the expansion. which resultsfrom heatingof the. brake/block .tends .to relieve itself. by excessive. swelling. in certain vlocal areas: and this. results in theconcentration of pressurein .those .areas and an extremely high energy dissipation. demand per unit of. area which is believed to beat least in part responsible for so-called thermal cracking of the. braking surfacewith which. the brake block. has frictional engagement;

Various methods have been tried to eliminate, or reduce this localization of pressure, such. as, foreXample,--slotting., the brake shoes or brake blocks I in. various manners, but. this .hasnot. been sulficiently efiective'to accomplish the. desired results. I have discovered .a novel means of eliminating the. difficulty: by; providing a. special form of brake block. mounted on its supporting head in'such manner astoavoid .developmentof these excessive pressures by permitting-thenceessary swelling orexpansion ,inthe brake. block to betaken upin suchmanner-asnot. to. interfere with the braking: effort. I have accomplished thisby providing arelief; groove at the back. of thebrake. block so that. a continuous space extends from one endof. the brakeblockto theother end thereofbetween said block and the supporting brake head the groove beingof-maximumdepth alongthemedian line of the. length of the block andbrakelieadand arcuatelytapering indepth at both-sides .01 said median line toward; the lateral. edges thereof, thus permittingmaximum flexing of the block at its midpoint. when loadede: WhileVI have-illustratedthis as a continuous channel; extending ;the-full length of,

point.

the block to aiiord a fluid passage between the brake headand the shoe ,.nevertheless, itis believed that the. primary area between the shoe-and thesupporting head to permit expansion or flowofthe brake, block.- material away from-theirictionsurface; It will be understood by those skilledinthe art that underloading conditions .such tion of the brake block-v may loaded as a beam withmaximum load-at itsm-id- With-a relief cavity provided. alongthe above-mentioned median line. and .of the form described, center blisters on thebrakeblock. are

largelyavoided and the. block is.permitted touas sume relatively even .wear .overtheuentirezarea. thereof so that the lifethereot isprolonged .and- It is. not be.- lieved essential that. the..passage .be. continuous. although this may facilitatescoolingras .by-fluid.

its usefulness .greatly. increased.

flowtherebetween. I have illustrated thissrelieved groove eitheras formed in. thebrake. head or in the brake block 01' shoe. In the drawings, Figure 1 isa .planyiew-v of.my.. novel. form.,.of

brake head and shoe assembly taken from the-lug side of the head where it ported- Figure 2 is an end View of-the. assemblyjshown in Figure 1, taken from the bottom .as seen there.-

may. be pivotally sup.-.

in, and Figure 31s asectionalview.throughthehead and-shoe takenapproximately in the radial plane indicated .by the line 37-3 of Figure 1.1

Figure .4 is. a plan view of my. novel form of brake block or brake shoe taken from the friction face thereof. Figures is an-end View taken 1 from the bottom as seen in Figured, and Figure 6 is a sectionalview takenapproximately in the radial plane bisecting the .shoeasindicatedby the line iii-.6 of Figure 4...

Figure? isa sectional .view. comparable to that of Figure 3, illustratinga modificationofmy invention.

Describing in detail my novelbrake head and brake shoe assembly, it will be notedthat I have illustrated my inventionas applied to a segmental type, so-called, wherein the brakehead and brake shoe assemblyis designed for application to one side of a rotatable brake drurnsuch asmay be utilized in railway equipment. The brake head, generally designated 2, of segmental form,

may be defined by. an outer circumference 4, an

inner circumference 6 andradial ends 8, 8; On the rear of the head maybe the spaced. lugs-Iii, l0 affording mounting meansv for the assembly, said lugs having aligned openings II,. I l bushed as at l2 (Figure 2) for accommodation of the supporting spindle.

On the oppositeiace of the head may be secured my novel form. of brake. block, generally designated I4, said block being secured tosaid function is .toprovide an as described, a sec-. be. considered tobe.

shoe may be filled, as well seen at "3 in the sectional view of Figure 3, and the brake block or having a plurality' shoe [4 is here illustrated as of spaced radial grooves 29, 20(Figure 4),, as .well as a circumferential length of the shoe and, of course, intersecting groove 22 extending thefull f the radial grooves 20, 20. Also, the shoe l4 may be relieved on its head-engaging face by a shallow groove 24, the cross-sectional contour of a which is perhaps best shown in Figures 3 and 6, where also the cavity 26 between the shoe and headis clearly illustrated. 1

The detail of my novel form of friction shoe [4 is shown in Figures 4, 5 and 6, wherein it may be notedthat the block isdrilled as at 28, 28 for the beforeementioned rivets I6, .16. The sectional view ,ofFigurefi is taken through one of the radial slots 20 so that therelative depth of the slots 20 and, 22 is well illustrated in said figure. The relieved. groove 24 shallow with an arcuate contour in section and extends for. the full length oftheshoe with the same ,contour throughout. While this is a. convenient manner of forming such relief as I have described, particularly from the standpoint of machining operations, nevertheless, 7 experiment hasindicatedthat any relief means suitable to admit the flow or expansion of the brake shoe material under sharp increments of temperature would. be satisfactory.

. The modification generally similar to that just described except that the brake head I02 is formed with a.con-' tinuous arcuate groove I04 extending the length thereof. in manner similar to that of the previous modification. In the modification of Figure '7 the brake shoe I06 is secured to the brake head 102,,

as described for the previous modification, bya series of countersunkrivets I98. I08, said rivets beingcountersunk in theishoe I06 to a point just, below the transverse slots H0. The longitudinal.

slot'll2 in the shoe I06 may be somewhat shallower, as in the previous. modification, and the rivet openingsmay be similarly filled or asat ||4.

It istobeunderstoodthat I do not wish to be limited by the exact embodiments of the device shown which are merely bywayof illustration and not limitation as various andother forms of thedevicewill, of course, beapparent to those skilled in the. art .without departing from the spirit of the invention or the scope of the claims.

Ielaim: r I i 1. A segmental brake head and shoe assemblyv comprising a rigid head having spaced lugs with aligned openings for reception of associated pivotal securing means, anda composition, brake shoe havinga fiat face in complementary engagement with the faceof said head, said flat face having-a relievedportion defining a shallow, ar-. cuate cavity between said head and shoe continuous from end to end thereof and suitable to accommodatethe flow of fluid means therebetween, said cavity.also serving to accommodate the expansive flow of the composition material of whichisaid shoe is composed ina direction toward said head and away from the friction surface of said shoe whereby substantially equalized pressure is Isecuredon-said friction surface, said shoe having a plurality of intersecting slots on the friction face thereof, said cavity extending is illustrated as relatively illustrated Figure .7 is.

plug ed.

7 aligned openings aligned openings for reception of associated piv- "otal securing means, and "shoe'having a flat face in complementary engagement with face having a r elieved portion ble'to accommodate the flow of fluid meirw from the braking surface of said block coinci- 4 approximately halfway across, the width of said shoe for the full length thereof.

2. A segmental brake head and shoe assembly comprising a rigid head having spaced lugs with a composition brake the face of said head, said flat defining a shallow, arcuate cavity between said head and shoe continuous from end to end thereof and'suitatherebetween, and a plurality of intersect slots of varying depth in the friction face of said shoe, said cavity being continuous from end to end of said shoe and extending across a substantial portion of the width thereof and having its greatest depth adjacent the middle ofsaid shoe and tapering therefrom to minimumdepth adjacent the opposite edges, said cavity being equal to at least one-third the area'of said shoe and lying along the median line of its length. 7

3. An assembly comprising a rigid brake head and a composition brake block secured thereto, adjacent the margins thereof, said blockhaving a. relieved portion intermediate said margins de fining a shallow arcuate cavity between said head and block and being of greatest depth in an area substantially medially between said margins and arcuately decreasing'in depth toward the same, said cavity being adapted to accommodate expansion of the material of said block in the regionof said cavity toward said head and away, from the braking surfaceof said block coincidentally with the expansion of saidsmaterial at said margins as said material is expanded by frictional development of heat under service con ditions,. whereby substantially uniform pressure is secured upon the entire braking surface of said block. H i .4. A segmental brake head and shoe assembly comprising'a rigid head having spaced lugs with for reception of associated pivotal securing means, and a composition brake shoe having a flat face in complementary engagement with the face of said head, said flat face having a relieved portion.defining a shallow, arcuate eavitybetween said head. and shoe continuous from end to end thereof and suitable to accommodate the flow of ,fiuid means therebetween, said cavity being a shallow, arcuate channel extendingfrom end to end ofsaid shoe adjacent the middle thereof and underlying a substantial portion of said shoe equal to at least one-third of the area thereof. 7 I 5. An assembly comprising, a rigid brake head and a composition brake block secured thereto adjacent the margins thereof, said head having a relieved portion intermediate said margins defining a shallow arcuate cavity between said head and block and being of greatest depth in an area substantially medially between said margins and arcuately decreasing in depth towardtheisame said cavity being adapted to accommodateexe pansion of the material of said block in the region of said cavity toward said head and away,

dentally with the expansion of said materialat said margins as said material is expanded by frictional development of heat under service conditions, whereby substantially uniform pressure is secured upon the entire braking surface of said block.

6. A segmental brake head and shoeassembly' comprising a rigid head member having spaced lugs with aligned openings for reception of associated pivotal securing means, and a composition shoe member having a flat face in complementary engagement with an abutting face of said head member, one of said faces having a relieved portion defining a shallow, arcuate cavity between said members continuous from end to end thereof and suitable to accommodate fluid flow therebetween, said cavity being centrally positioned on said face and covering a substantial portion of the area thereof and having its great,- est depth adjacent the median line of said face andarcuately tapering in depth at both sides of said median line, whereby, upon application of a load to said brake head and shoe assembly, substantially pressure is secured upon the entire friction face of said shoe.

7. An assembly comprising a rigid brake head member and a composition brake block member secured thereto adjacent the margins thereof, one of said members having a relieved portion intermediate said margins defining a shallow arcuate cavity between said members and being of greatest depth in an area substantially medially between said margins and arcuately decreasing in depth toward the same, said cavity being adapted to accommodate expansion of the ma terial of said block member in the region of said cavity toward said head member and away from the braking surface of said block member coincidentally with the expansion of said material at said margins as said material is expanded by frictional development of heat under service conditions, whereby substantially uniform pressure is secured upon the full braking surface of said block member.

8. An assembly comprising a rigid brake head and a composition brake block secured thereto along the margins thereof, said block having a relieved portion between said margins defining a shallow arcuate cavity between said head and block to permit expansion of the material of said block in the region of said cavity toward said head and away from the braking surface thereof coincidentally with the lateral and longitudinal expansion of said block upon braking application of said assembly and development of heat upon such braking application, said cavity extending over at least one third of the area of said block remote from the lateral margins thereof and having its greatest depth adjacent the median line of the length of said assembly, and a slot in the braking surface of said block extending along the median line of the length of said block.

9. A brake head and shoe assembly comprising a rigid brake head member and a composition brake block member secured thereto adjacent the margins thereof, one of said members having a relieved portion intermediate said margins defining a shallow arcuate cavity between said members and being of greatest depth in an area substantially medially between said members and arcuately decreasing in depth toward the same, said cavity being adapted to accommodate expansion of the material of said block member in the region of said cavity toward said head member and away from the braking surface of said block member coincidentally with the eX- pansion of said material at said margins as said material is expanded by frictional development of heat under service conditions, whereby substantially uniform pressure is secured upon the entire braking surface of said block member, and a plurality of intersecting slots on the braking surface of said block member, at least one of said slots being disposed adjacent the greatest depth of said cavity.

10. A brake head and shoe assembly comprising a riveted head member and a composition brake shoe member secured thereto, one of said members having a relieved portion defining a shallow, arcuate cavity between said members for accommodation of expansion and flow of said composition material under service conditions, said cavity extending for the length of said assembly upon both sides of the median line thereof and having its maximum depth adjacent said median line and arcuately decreasing in depth at both sides thereof to accommodate maximum expansivity of said shoe member along said median line when under stress and thereby reducing the expansion of said shoe member toward the lateral and longitudinal edges thereof.

11. A brake head and shoe assembly comprising a supporting member with a composition supported member, and a relieved portion on one of said members adjacent the other defining a cavity therebetween, said cavity being a shallow, arcuate channel along the length of said members and having an area approximately equal to that of the abutting faces on said members and being positioned along the median line of the length of said assembly and having its-maximum depth adjacent said median line to accommodate maximum fiexing and expansivity of said supported member along said median line when placed under stress in normal loading.

12. A brake head and shoe assembly comprising a supporting member with a composition supported member, and a relieved portion on one of said members adjacent the other defining a cavity therebetween, said cavity being a shallow, arcuate channel along the length of said members and having an area approximately equal to that of the abutting faces on said members and being positioned along the median line of the length of said assembly and having its maximum depth adjacent said median line and arcuately tapering in depth therefrom toward the lateral edges of said members to permit substantially uniform flexing and expansivity of said supported member, whereby relatively equal pressure is secured on the entire friction face thereof when the same is placed under normal loading stress.

CARL E. TACK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,513,864 Schmidt Nov. 4, 1924 1,847,680 Thompson Mar. 1, 1932 2,150,186 Pope Mar. 14, 1939 2,163,884 LaBrie June 27, 1939 2,236,311 Eksergian Mar. 25, 1941 2,239,574 Schell Apr. 22, 1941 2,348,077 Ledwinka May 2, 1944 FOREIGN PATENTS Number Country Date 324,455 Great Britain Jan. 30, 1930 488,382 Great Britain July 6, 1938 Certificate of Correction Patent No. 2,438,483. March 23, 1948.

CARL E. TACK It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 16, before the Word pressure insert equal;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of December, A. D. 1948.

THOMAS F. MURPHY,

Assistant Gommz'ssz'oner of Patents. 

